At XCritic we aren't huge fans of many personals site. Many take so long to hook up with anyone or are completely filled with people who are looking for a soulmate rather than someone to have a nice romp with.
We were extremely impressed by PinpointsX when it launched earlier this year (read our launch review). PinpointsX uses an iPhone app which lets you hook up with people in real time. No endless emails, texts or calls. You can find people near you, right now who are looking to have fun.